core: Fix compile fail

Since add explanation in core/sys/, But this explanation have not
been used "/* */" grammar.

Signed-off-by Zhong Hongbo <bocui107@163.com>
hal: clear code format

Signed-off-by Zhong Hongbo <bocui107@163.com>
rf230: use local_irq_save/restore replace old defined

The old global irq disable/enabled is limited.
AVR_ENTER_CRITICAL_REGION/AVR_LEAVE_CRITICAL_REGION. and
local_irq_save/restore can use any location in the program.

Signed-off-by Zhong Hongbo <bocui107@163.com>
AT86RF230: Analysis the initialization in mac and phy for IEEE802.15.4

Signed-off-by Zhong Hongbo <bocui107@163.com>